Process of manufacturing an optical element



Nov. 21, 1950 P. 7M. VAN ALPHEN 2,530,742-

PROCESS OF MANUFACTURING AN OPTICAL ELEMENT Fild Jan. 14, 1946 HETER MARTINUS Z4NALRHEN INVENTOR.

ATTORNEY Patented Nov. 21, 1950 WPROCESS' 0F ANUFAG URING AN ,YOPTICAL ELEMENT Pieter=Martinus van Alphm Eindhoven, Nether- 'lands; as'si gnor by mesne assignments, t6 Hafti tordsNa-tional Bank and Trust Company, Hart- 'ltord, Gonn., asjtrllstee "fApplicajtionJanuafy 14, was; Serial Noifl6 i1179 "In the" Netherlands my 19,-;1941

: aSection v1-, Public Law cam-Augu t's, 194s q Patenteexpires. July 1-9, F1961 i1. njthep'rior art'as ekemplifiedby U. S. Patent .2Y,3.32,93Qt6 Herre fiinlaffor an'fOptical Eleit. is suggested.byithempeitenteeito make ent, .jas .a; lens, jfrom; a substance hl e.irl so1i1tion. LBy proceeding hasfgbeen found. possible to aliufa'ctuige,iiforfiexal iiple' lenses .with ,a 7 very aecura cyin; a 'comparaitivelysimple manner without" the uBI01i grinding; operations, 'In this se nse, is made [of agmo'uld into. which. a: s'oluonfbf a, substancefl .gelatinisable .in-sohition, is

this, substance, has been gelatblntion and dried .pp and a n ed ),-Qthe, element which. has gjjthgn acqj I dfitsQdsired shape J may .be removed jf rcml'lthe' mould. v a I, c cording;.it o this. .m'eth'odyusefis .made or the =phermmenonl'tha he "gel...whlch' is. separated in mama tirlom e oliztion .bfflthe. gelatlnisable 1th elasticity; contracts during drying up. L'Ihe gree ofleohtta'ctiOnQwhich occu'rs may; be .fully E egntr' llemby. means .of .awsiiitable choice ofxthe -conjcehtra'tion ofiihe gelatinisable substancepresnt .jin the sohition Iinjthe; associated solvent. In tithe cas oi'gelatinefithisl contra'otionmay be .be-

tween actorsjbflthe o'tdenlof .magnltiideof 3., and {.59. I ,mgi to'fltliis contraction}the .matrixlused fg!" thegnannfactureofjhthe. o fit ical element ,concernfedmay.exhibitfdimensions which are much gcge'r. ,than'fthe ,jdimens'ions ,bf,itheIjobj.ect, to] 'be vjustvmentioned, preyents .contractipnln the radial Claims. (0151 18 5B) i2 -Dliocess .the optical element: to? be; manufactured is. hardenedg if- ,desired, which; operation takes place during orafterdrying, y

,flhel.ppsentgnvehtibn:315d relates toja j rocess of manufacturing an, gpticalfelement jas a vlens, f1 ,om1 ,the,above=mentioned substances: in. which, however, the body in the gel 'statewhijch hasto constitut th lensisetfirst. artificia y hard ed n omy. t reatterldfiedl-jTne .methodwbf.hardenin gecpordingQ-to .,pre s,e'n t inventicn has-Jthej;fol1owing.a anta s vzqela'.tively, to them 'hodjoi, hardening described in theaforesaidp .."Pa'1 ,1.,1t 'NQ; 2",332930.

,As has been; ound by applicantgin the..first lblacefthe. li it; bf'istretchin fstrain, bith jf ar to. be manufactured exhibitslapge difierences'in "thickness, asfis thecaseffor example, when this element. exhibits.one ox-two; asph'erlcal bounding surfaces and thilsdxi'es up unequally. When the material is dried. inf the unhardeened state, the tensions due to contraction may lead toitearsor undesirable permanent'deforxnation in the surface .of ijtheiib dy which hasito constitute the ,pnt cal element. 'jrhese render the el me (con- J 'erned less adapted fp ljthe pu p se? p ope .LTQW, .byjp c ed hgii rr, acc rdanc wi h heinvenfim andjiat first hardeninggandsubsequently; dryin thedimit of stietch'edzstrzin'of. th materi l. d in d yin liesfl ilffi etit y hi h-tha th pos bili y of; tears and nmlesirable permanent deformationsf.is pragti'callysprecluded., V

Eur h rmore; due; to th dif rences in hickiness, s ich ppticlal elements will never dryequally on. the. whole. For ,examp1e,jat a, given, moment theithlnnestplace om lens to be manufactured jis thoroughly;dry-whereas onjthe thickest places 7 .the 'snperficialjpants areddry but, the, .more ,in-

3 mms. In this case unequal drying occurs, which might lead to rings produced on the element due to drying. If, however, use is made of the process according to the invention, it is possible for the undried body which is hardened to be dried at a temperature higher than if the optical element is not hardened. Thus, the advantage is obtained that the occurrence of rings due to drying is substantially avoided due to the quicker drying. According to the invention, the hardening agent, for example formalin, may be added to the liquid from which the optical element concerned is to be manufactured. This is in general simpler than the arrangement of the undried optical element in an atmosphere of the hardening agent.

The substances from which the optical element according to the invention may be manufactured and which are consequently gelatinisable in solution may contain organic components, such as gelatine, agar-agar and pectine. It is also possible for these substances to contain inorganic components, such as silicates or aluminium oxides, with or without glycerine, to assist in the optical homogeneity of the optical element concerned. The solvent is chosen in accordance with the substance to obtain a solution which is gelatinisable. For gelatine use ma be made, for example, of water as a solvent. The hardening of the body in the gel state which has to constitute the optical element may be effected, for example, with formalin.

It has been found by applicant that the method according to the invention is particularly adapted for the manufacture of an optical element in which at least one bounding surface in a section through the axis of the element exhibits a curve of a fourth or a higher degree.

The mould previously referred to may have, for example, a base plate of metal or glass. In the latter case it is conceivable that this base plate, after the manufacture of. for example, a lens, serves as a carrier for this lens.

In the accompanying drawing:

Figure 1 is a cross-sectional view of apparatus which may be used in the process of constructing an optical element in accordance with the invention; and

Fig. 2 is a cross-sectional view of an optical element produced by the invention.

Referring now to Fig. 1, a plate I!) of glass has positioned over it a template I2, constructed to be hollow. Template I2 is provided with two pipes l3 and I4 for the ingress and egress of a temperature controlling liquid; for example, water. The template I2 also has a central bore I5 which serves to supply material I6 from which the body I I is to be made. The material I6 may consist, for example, of water in which gelatin is dissolved in a given concentration corresponding to the desired subsequent contraction and in addition, a sumcient amount of formalin to act as a hardening agent. By means of the water which flows through it, the-template I2 is maintained at a temperature at which the gelatin just remains in the dissolved state. By gradually reducing the temperature of the template (and also of the glass plate if required), the solution I6 is gelatinized and a gel is produced which is possessed of resilience accompanied b rigidity. The template I 2 can then be removed and the material I6 remains on the plate IEI. As the material I6 already contains the formalin, it may b heated to cause drying with comparative rapidity and it is unnecessary after the substance is completely dried to harden it in a, formalin atmosphere. As the substance I6 shrinks and dries, it assumes the shape of the element I I shown by dotted lines and at the same time, the substance adheres to the plate I9 so that no contraction occurs radially. The edge of the gelled material may be severed circumferentially along the lines I8.

Thus is obtained the optical element I I adhering to the plate H) as shown in Fig. 2.

What I claim is:

l. A method of manufacturing an optical element from a material which is gelatinizable in solution, comprising the steps of placing a quantity of the material in solution upon the surface of a support to which the gelled material adheres, forming the said material in solution into a gelled mass having predetermined thickness and length dimensions, artificially hardening said mass by the action of a hardening agent, and thereafter desiccating the so hardened mass to reduce its shape to that of the optical element.

2. A method of manufacturing an optical element from a material which is gelatinizable in solution, comprising the steps of shaping a quantity of the material into a mass having a form approximating that of the optical element, hardening the so-formed mass by the action of a hardening agent, and drying the so-formed and so-hardened mass to reduce its size and change its shape to that of the optical element.

3. A method of manufacturing an optical element from a material which is gelatinizable in solution, comprising the steps of placing a quantity of the material in solution upon the surface of a support to which the gelled material adheres, forming the said material in solution into a gelled mass having predetermined thickness and length dimensions, artificially hardening said mass by the action of a hardening agent, and thereafter heating the so-hardened mass to desiccate the same with substantial uniformity.

4. A method of manufacturing an optical element from a material which is gelatinizable in solution, comprising the steps of adding a hardening agent to a quantity of the material in solution, placing a quantity of the so-formed material upon the surface of a support to which the gelled mass adheres, forming the said material into a gelled mass having thicknesses and thickness variations substantially proportional and greater than those of the element to be formed, said gelled mass having length dimensions substantially the same as those of the element to be formed, the said thickness variations being greater than about 3 mms., allowing the mass to become hardened by the action of the hardening agent, and thereafter desiccating the so-hardened mass while on the support, whereby the thicknesses and thickness variations of said mass are reduced to the element to be formed and the said length dimensions are maintained substantially constant.

5. A method of manufacturing an optical element from a material which is gelatinizable in solution, comprising the steps of placing upon the surface of a support to which the gelled mass adheres a quantity of the material in a solution in which is incorporated a hardening agent, forming the said material in solution into a gelled mass, allowing the gelled mass to become hardened by the action of the hardening agent, and desiccating the so-hardened mass while on the support.

6. A method of -manufacturing an optical element from a material which is gelatinizable in solution, comprising the steps of placing upon the su faee of a support to which the gelled ma.- terial adheres a quantity of xnaterial in a solution to which has been added a. hardening agent, forming the said material in sai solution into a gelled mass, hardening the so-f ed; gelled mass by the action of the harde fig agent, and subsequently heating the so-herde mass to desiccate the same with substantial iformity.

' PIETER MARTINUS m ALPHEN.

REFERENCES CITE D The following references'ere' of record in the file'of this patent:

Number UNITED STATES PATENTS Name Date Leuchter .4 Oct. 29, 1907 Straubel Aug. 29, 1939 Rinia Oct. 26, 1943 Rinia. May 29, 1945 FOREIGN PATENTS Country Date France Dec. 5, 1941 

1. A METHOD OF MANUFACTURING AN OPTICAL ELEMENT FROM A MATERIAL WHICH IS GELATINIZABLE IN SOLUTION, COMPRISING THE STEPS OF PLACING A QUANTITY OF THE MATERIAL IN SOLUTION UPON THE SURFACE OF A SUPPORT TO WHICH THE GELLED MATERIAL ADHERES, FORMING THE SAID MATERIAL IN SOLLUTION INTO A GELLED MASS HAVING PREDETERMINED THICK- 